US2380520A - Borehole indicating apparatus - Google Patents

Description

July 31, 1945. L b HASSLER 2,380,520

BOREHOLE INDICATING APPARATUS Original Filed April 24, 1942 2 Sheets-Sheet 1 F593 Bg his AHforneg2 A July 31, 1945. G. HAssLER 2,380,520

BOREHOLE INDI CATING APPARATUS Original Filed April 24, 1942 2 Sheets-Sheet 2 Plaie 5upp|g Volfage Murfivibrvmr Fig. 4

Fig. 6

lnvenor: Gerold L Hassle Patented July 3l, 1945 BREHOLE INDICATING APPARATUS Gerald L. Hassler, Altadena, Calif., signor to Shell Development Company, San Francisco,

Calif., a corporation of Delaware Original application A 440.405. Divided and 1944, Serial No.

2 Claims.

The present invention relates to an apparatus for transmitting signals to the surface from an instrument capable of detecting, observing or measuring the nature of the phenomena occurring in aborehole or the nature and characteristics of the formation traversed by said borehole, and pertains more particularly to apparatus for transmitting continuously a signal or a series of signals or vibrations through equipment or material in the borehole. such as the mud fluid, drill pipe or the like.

The present application is a division of my cpending application Serial No. 440,405,1lled April 24, 1942, now Patent No. 2,352,833.

Various instruments have been proposed for measuring various properties in a borehole, but these devices and methods are open to various objections. Since, when using self-contained recording instruments, there is considerable delay before the record is available to the driller, it has been proposed to use electrical conductors, sometimes together with synchronous motors, such as Selsyn motors and the like, to indicate immediately at the surface the measurements taken by the instrument. Due to the high cost of multiwire insulated cables and their limitations with regard to their use in deep boreholes. such systems in many cases cannot be economically employed.

It is therefore an object of the present invention to provide a system for continuously indicating at the surface desired characteristics in a borehole without the necessity of using electrical cables or other directly-connecting means.

It is another object to provide a system comprising means to detect or measure a desired characteristic or feature in the borehole, means responsive to said measurements to transmit vlbratlons through the mud fluid or along the drill stem to the surface, and detecting and. indicating means at the surface.

It is another object of this invention to provide an apparatus for transmitting to the surface de-` cipherable signals responsive to the drilling variables such as of weight on the drill bit, rotational rate of the bit, bottom hole temperature and pressure, etc., whereby the driller may adjust said variables to their optimum values.

It is a further object to provide a method of and apparatus for simultaneously measuring the resistivity of the formation and the inclination of the borehole and obtaining at the surface indications proportional to said measurements without the use of an electrical cable or conductors extending down into the well.

pril 24, 1942, Serial No.

this application March 25.

(Cl. 'I3-151) Other objects will be readily apparent from the following description taken in reference to the drawings, which illustrate several applications of the present method and. apparatus therefor. In the drawings,

Fig. 1 is a longitudinal sectional view of an embodiment for simultaneously reporting the resistivity of the formation and the inclination oi' the borehole.

Fig. 2 is a cross-sectional view taken along the line 2 2 in Fig. 1.

Fig. 3 is a cross-sectional view taken along the line 3-3 in Fig. l.

Fig. 4 is a diagram of a preferred electrical circuit for actuating the wave transmitter.

Fig. 5 is a schematic longitudinal view of the instrument in position in the borehole together with the surface equipment.

Fig. 6 is an illustrative portion of the record chart obtained at the surface.

Generally, the present invention resides in the new apparatus for conducting continuously or for a predetermined period informative or control signals between the surface of a well and a device. such as a measuring or surveying instrument, in the borehole by means of vibrations, such as pressure or true sound waves, transmitted through usual material or equipment present in the borehole, such as through the fluid in the borehole, along the drill stem or pipe or any other suitable sound conducting channel, etc. The present apparatus for obtaining indications at the surface of desired measurements in the boreholes eliminates the use of expensive special signal conducting means, such as electrical cables, insulated drill strings and the like, whicntake considerable time to properly position in the borehole. Likewise, by means of the present invention, the measurements are to the driller or operater at the well head so that he may more accurately and efficiently control the drilling variables, such as the weight or load on the bit, rotational rate of the drill bit. bottom hole temperature and pressures, etc., and the positioning of various tools such as packers, liners, etc., as well as other operations, which depend on the nature of the borehole.

Suitable vibrations include sound waves' or nonaudible waves of lower or higher frequency which may be transmitted by equipment in the borehole, such as drill pipe, casing or iluid in the borehole. Various means may be used to initiate the desired control or informative vibrations.v 'u For example, various horns, clickers. and other instantly availablesimilar devices may be used to produce the desird sound waves.

Various instruments and devices can be used with the principle of communication of the present invention. Thus, for example, a temperature or pressure measuring instrument containing a temperature or pressure-responsive vibration sender may be lowered by means of a wire line down through the drill string while drilling without the use of cumbersome and expensive electrical cables. 1i' desired, such instruments may be incorporated in the drill collar or bit. Batteries or a rubber propeller in the mud stream may be used to actuate said instrument.

The present invention is concerned with a device for transmitting sound wave signals through the mud fluid column or drill pipe, which signals may be used to indicate at the surface, for example, both the resistivity of the formation penetrated and the inclination of the borehole.

To accomplish this, a pressure wave transmitter, together with resistivity and inclination measuring instruments and batteries or a small mud stream generator yielding, for example, 100 watts, are all placed in an insulated section or stand oi' drill collars. Since the drill pipe conveys energy in flowing mud and is capable of carrying signals in vibrations of the mud, it is necessary to insulate electrically only enough of the drill pipe to isolate the formation being meas'- ured, whereby there is eliminated the use of insulated drill pipe, which is expensive to make and handle.

Briefly, the device simultaneously measures the electrical resistance of the formation and the inclination of the bit and drill collar and reports these measurements to the surfaces by a series of sound pulses sent through the drill pipe by the use of a sound transmitter controlled by an electrical analogue of the mechanical weight reporting device described hereinabove.

Referring to Figs. 1 to 6 of the drawings, one embodiment of a device suitable for this purpose comprises a bit |50 serving as the electrode which is attached to the lower end of the drill collar |5| by means of a' connector or substitute |52 of insulating material such as Bakelite or the like andl 't usual substitute |53. The bore |54 in the drill collar is enlarged in its upper portion as at |55 and this enlarged portion |55 contains a transmitter. such as a horn |55 of about 100 cycles, in uppermost position, a mud turbine, |51 preferably with rubber impeliers |55, connected to a suitable electrical current generator |55 by means of gears |55, and therebelow in a fluid tight housing |54 a pendulum |55 hung by a ball and socket suspension |55. The pendulum |55 is caused to hang .vertically downward in spite of the vibration and rotation of the drill collar |5| by applying thereto suitable damping forces, such as by means of a contained free gyroscope |51 in oil. The pendulum |55 forms or carries the ogo ternately nre and suppress one another.

While one of the two tubes is passing plate current, which may be, fo'r example, for a length of time proportional to the resistivity of the formation. the transmitter or horn |55 is actuated and sends a blast, of sound or pressure waves up the drill pipe. while the other or the tubes is bassins plate current, which in this-case is for a length of time in proportion to the inclination of the drill collar, the horn |55 is silent. These alternate periods of sound and silence may be translated by a suitable instrument at the surface into continuous curves drawn against depth.

Referring to the diagram of Fig. 4, a preferred form of the indicating circuit comprises a high frequency generator |5| from which a high frequency current flows to the ground at |52 through condensers |85 and |55, the latter being the variable condenserl |55 operated by the pendulum |55. The voltage developed across the variable condenser |55 is approximately inversely proportional to the capacity of condenser |55. which capacity decreases with increasing inclination of the instrument. The A. C. voltage across condenser |55 is rectied by diode tube |55 and n1- tered by resistors |55 and |51 and condensers |55 and |9|la so that the voltage a across condenser |5511 is D. C. and positive, and increases with an increase in the angle of inclination of the instrument. In a somewhat similar manner, a positive D. C. voltage b is obtained across condenser |55b which increases with an increase in the resistivity of the formation by drawing its controlling voltage from a suitable circuit comprising a lter and a detector furnishing a voltage indicating the resistivity, such as for example, shown in Karcher 1,927,664 or Leonardon 2,249,769. A multivibrator comprises the central portion of the circuit as indicated in Fig. 4, and includes a pair of gas triode movable element of a variable condenser |55, y

which forms a part of the indicating circuit. The remainder of the indicating circuit may be suitably arranged for the sake of balance of the drill collar |5| in a pair of tubular housings |1| positloned in recesses |12 in the inner walls of the drill collar |5|, as shown most clearly in Fig. 2.

Briefly the indicating circuit may comprise a multivibrator circuit so arranged that an ineluded pairof triode radio tubes are each separately timed by the quantities being measured, namely. the resistivity of the formation and the tubes |52a and |52b `and resistances |53a and |5311. a and b are the grid bias voltages for the multivibrator and control itstwo periods in the following manner.

At a certain time, tube'- |52a is carrying plate current and-tube |52b is .blocked by a highly negative grid voltage which may be designated as Gb. 'Ihis voltage. Gb, gradually decreasesin magni- 'tude due to the current from condneser isllb through resistor l'b; After the grid voltage Gb passes the cutoff valve, tube |52b fires. rapidly lowering the grid voltage Ga of tube |52a. Suddenly tube |52b starts carrying the maximum current and its plate voltage drops to zero, while tube |52a blocks, its plate potential Jumping up to the plate supply voltage.

The grid voltage Gb for tube |52b remains sufflciently positive so thaty the plate current of tube "2b is limited almost entirely by the plate re` sister |5lb and is but little affected by changes in the grid voltage Gb, until after the grid voltage Ga'for the tube Illa has passed cutoff. Then the rapid drop .in plate voltage of tube vIlla quickly pulls the gxid voltage Gb of the tube |52b down to the point at which effective control beginsand the sudden Jump occurs. HenceV the length of the integral (Jump to, jump) during which the grid voltage Ga to tube |52a is negativeis primarily determined by the time required for current from condenser |50a through resistor |55a to raise grid voltage Ga to cutoff. This depends on the coupling condenser capacity, the resistance of resistor Illa and the cutoff grid voltage, all oi' which are constant, and upon the inclination of the borehole, respectively, and algrid bias voltage a and the peak negative value of grid voltage Gajust after the jump. The latter in turn is determined by the size of the jump in plate voltage of tube |9221 which is substantially constant, and by the Value of grid voltage Ga just before the jump which increases with the grid bias voltage a. Increasing grid bias voltage a therefore increases theI magnitude of the negative peak of the gridvoltage Ga and also increases the rate of rise after the peak. Both of these changes reduce the time required for grid voltage Ga to rise to cutoff, and hence increasing grid bias voltage a reduces the length of the interval from jump to jumpfor tube I92a. Likewise, increasing the grid bias voltage b reduces the length of the interval for tube |921), during which grid voltage Ga for tube |92a is positive. The two intervals for the tubes |92a and |92b may therefore be used tc indicate the inclination and resistivity, respectively.

Theihorn |56, or other suitable generator of pressure waves in the drilling iiuid, is controlled by a relay` |95 connected to the plate circuit of tube |92a so that the horn |56 alternately is operated for the interval from jump to jump for tube |92a and is off for the interval for tube At the surface is a sufficiently sensitive recording receiver |96 (Fig. 5) of pressure waves, such as sound waves, tuned to the frequency of the hornv |56. The receiver |96 may be connected to the mud hose swivel |91, as shown in Fig. 5, to receive waves traveling up through the drilling fluid in the drill pipe. However, if desired, the receiver |96 may be placed to pick up waves in the rock or ground at a quiet location some distance away Ifrom the drilling rig, when, for example, there are used sound or pressure waves of a frequency that does not stay confined in the pipe.

As shown in Fig. 6, the record chart |98 produced by the recording receiver |96 indicates by means of the length of the dashes and the length ofthe spaces between the dashes the values of the inclination of the borehole and the resistivity of the formation, respectively.

As will be apparent, various other modications of this device may be readily made without de- Patent No. 2,380,520.

GERALD L. VHASSLER It is hereby certified that errors appear in parting from the spirit of the invention. Thus, although the preferred embodiment of this instrument described above shows a simplified form of resistivity measurement wherein only current electrodes are used, other arrangements can be used.

I claim as my invention:

1. In a system for continuously obtaining at the surface of a well indications of two independent well borehole variables, the combination of a clrill string adapted to be lowered into the borehole, separate measuring means in the lower portion of said drill string for each of said variables,

and means contained in the lower portion of theI the sound signals from said transmitter.

2. In a. system for continuously obtaining at the surface of a well indications of the inclination of the well and of the resistivity of the formation adjacent the drill bit, the combination of drill string adapted to be lowered into the borehole, a drill bit insulatedly attached to the lowerI end of said drill string, formation-resistivity measuring means in the lower portion of said drill string and electrically connected to said drill bit, inclination-responsive means in the lower portion of said drill string, and means contained in the lower portion of the borehole for sending indications of the resistivity measurement and the borehole inclination, said means comprising a power source, a sound transmitter, and an electrical circuit for timing the periods of actuation and silence of said transmitter in response alternately to the magnitude of said resistivity measurement and said borehole inclination, and means at the well surface for receivingl and recording the sound signals from said transmitter.

GERALD L. HASSLER.

Qerticate of Correction July 31, 1945.

the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 50, for valve read value line 66, for integra read interval; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oice.

Signed and sealed this 8th day of October, A. D. 1946.

` LESLIE FRAZER,

First Assistant Uommzssz'oner of Pa'tents.

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